A rare association between leukocyte adhesion deficiency type I and psoriasis in humans

Variable CD18 expression in a 22-year-old female with leukocyte adhesion deficiency I: Clinical case and literature review

Key Clinical Message

Partial leukocyte adhesion deficiency type 1 (LAD-1) deficiency is extremely rare condition with milder infectious manifestation and immune system imbalance leads to increased risks of autoinflammatory complications, such as pyoderma gangrenosum, that can be triggered by trauma or pregnancy. In patients with spice-site ITGB2 variants, partial expression can occur due to different β2 integrin isophorms expression.

Abstract

LAD-1, OMIM ID #116920 is a rare, autosomal recessive disorder that results from mutations in the ITGB2 gene that encodes the CD18 β2 integrin subunit. According to the CD18 expression, LAD-1 is categorized as severe (<2%), moderate (2%-30%), or mild (>30%). Here, we describe a 22-year-old female, who presented with inflammatory skin disease and oral cavity, as well as respiratory tract infections during the first year of life. LAD-1 was diagnosed at the age of 2 years by low expression of CD18 (1%). Whole-exome sequencing identified homozygous c. 59-10C>A variant in the ITGB2 gene. Despite severe phenotype, the patient survived to adulthood without hematopoietic stem cell transplantation and became pregnant at the age of 20 years, with pregnancy complicated by a pyoderma gangrenosum-like lesion. During her life, CD18 expression increased from 1% to 9%; at 22 years of age, 5% of neutrophils and 9% of lymphocytes were CD18+. All CD18+-lymphocytes were predominantly memory/effector cytotoxic T cells. However, revertant mosaicism was not being established suggesting that CD18 expression variability may be mediated by other mechanisms such as different β2 integrin isophorms expression.

The Role of LFA-1 for the Differentiation and Function of Regulatory T Cells—Lessons Learned from Different Transgenic Mouse Models

Regulatory T cells (Treg) are essential for the maintenance of peripheral tolerance. Treg dysfunction results in diverse inflammatory and autoimmune diseases with life-threatening consequences. β2-integrins (CD11a-d/CD18) play important roles in the migration of leukocytes into inflamed tissues and cell signaling. Of all β2-integrins, T cells, including Treg, only express CD11a/CD18, termed lymphocyte function-associated antigen 1 (LFA-1), on their surface. In humans, loss-of-function mutations in the common subunit CD18 result in leukocyte adhesion deficiency type-1 (LAD-1). Clinical symptoms vary depending on the extent of residual β2-integrin function, and patients may experience leukocytosis and recurrent infections. Some patients can develop autoimmune diseases, but the immune processes underlying the paradoxical situation of immune deficiency and autoimmunity have been scarcely investigated. To understand this complex phenotype, different transgenic mouse strains with a constitutive knockout of β2-integrins have been established. However, since a constitutive knockout affects all leukocytes and may limit the validity of studies focusing on their cell type-specific role, we established a Treg-specific CD18-floxed mouse strain. This mini-review aims to delineate the role of LFA-1 for the induction, maintenance, and regulatory function of Treg in vitro and in vivo as deduced from observations using the various β2-integrin-deficient mouse models.

Pyoderma Gangrenosum with an Underlying Leukocyte Adhesion Deficiency Type 1 (LAD-1) and Pregnancy in the Shade of COVID-19 Epidemic: A Patient and Physician Experience

In the first part of this article, the anonymous patient diagnosed with leukocyte adhesion deficiency type 1 (LAD-1) and pyoderma gangrenosum (PG) discusses her experience of her medical history and treatment in a foreign country during her pregnancy and the coronavirus disease-19 (COVID-19) pandemic. The patient’s dermatologists, immunologist, and diagnostician refer to the epidemiology, genetics, diagnosis, morphologic manifestations, including skin lesions, treatment, and prognosis in LAD-1. The patient’s diagnostic and therapeutic process was discussed in the last part of this paper.

Distinct Effects of Integrins αXβ2 and αMβ2 on Leukocyte Subpopulations during Inflammation and Antimicrobial Responses

Integrins α_Mβ₂ and α_Xβ₂ are homologous adhesive receptors that are expressed on many of the same leukocyte populations and bind many of the same ligands. Although α_Mβ₂ was extensively characterized and implicated in leukocyte inflammatory and immune functions, the roles of α_Xβ₂ remain largely obscure. Here, we tested the ability of mice deficient in integrin α_Mβ₂ or α_Xβ₂ to deal with opportunistic infections and the capacity of cells derived from these animals to execute inflammatory functions. The absence of α_Mβ₂ affected the recruitment of polymorphonuclear neutrophils (PMN) to bacterial and fungal pathogens as well as to model inflammatory stimuli, and α_Mβ₂-deficient PMN displayed defective inflammatory functions. In contrast, deficiency of α_Xβ₂ abrogated intraperitoneal recruitment and adhesive functions of monocytes and macrophages (Mϕ) and the ability of these cells to kill/phagocytose Candida albicans or Escherichia coli cells both ex vivo and in vivo During systemic candidiasis, the absence of α_Xβ₂ resulted in the loss of antifungal activity by tissue Mϕ and inhibited the production of tumor necrosis factor alpha (TNF-α)/interleukin-6 (IL-6) in infected kidneys. Deficiency of α_Mβ₂ suppressed Mϕ egress from the peritoneal cavity, decreased the production of anti-inflammatory IL-10, and stimulated the secretion of IL-6. The absence of α_Xβ₂, but not of α_Mβ₂, increased survival against a septic challenge with lipopolysaccharide (LPS) by 2-fold. Together, these results suggest that α_Mβ₂ plays a primary role in PMN inflammatory functions and regulates the anti-inflammatory functions of Mϕ, whereas α_Xβ₂ is central in the regulation of inflammatory functions of recruited and tissue-resident Mϕ.

Reduced CD18 levels drive regulatory T cell conversion into Th17 cells in the CD18hypo PL/J mouse model of psoriasis

Defective development and function of CD4(+)CD25(high+)Foxp3(+) regulatory T cells (Tregs) contribute to the pathogenesis of psoriasis and other autoimmune diseases. Little is known about the influence of adhesions molecules on the differentiation of Foxp3(+) Tregs into proinflammatory Th17 cells occurring in lesional skin and blood of psoriasis patients. In the CD18(hypo) PL/J mouse model of psoriasis, reduced expression of CD18/β2 integrin to 2-16% of wild-type levels is associated with progressive loss of Tregs, impaired cell-cell contact between Tregs and dendritic cells (DCs), as well as Treg dysfunction as reported earlier. In the present investigation, Tregs derived from CD18(hypo) PL/J mice were analyzed for their propensity to differentiate into IL-17-producing Th17 cells in vivo and in in vitro Treg-DC cocultures. Adoptively transferred CD18(hypo) PL/J Tregs were more inclined toward conversion into IL-17-producing Th17 cells in vivo in an inflammatory as well as noninflammatory environment compared with CD18(wt) PL/J Tregs. Addition of neutralizing Ab against CD18 to Treg-DC cocultures in vitro promoted conversion of CD18(wt) PL/J Tregs to Th17 cells in a dose-dependent manner similar to conversion rates of CD18(hypo) PL/J Tregs. Reduced thymic output of naturally occurring Tregs and peripheral conversion of Tregs into Th17 cells therefore both contribute to the loss of Tregs and the psoriasiform dermatitis observed in CD18(hypo) PL/J mice. Our data overall indicate that CD18 expression levels impact Treg development as well as Treg plasticity and that differentiation of Tregs into IL-17-producing Th17 cells is distinctly facilitated by a subtotal deficiency of CD18.